Maybe, but the other "only" reason is patronage. State store employees are state employees, and the jobs are given out by the local politicians. It would be a huge loss of power for those politicians.The state store system generates an annual profit of around 100 million dollars. The only reason the state store system hasn't been kicked to the curb is because there has not been a satisfactory proposal put on the table that has a privatized liquor system generating as much state revenue as the current system.
Even notice that state store employees look like toll collectors on highways (old and bored)? They are products of the same system.